The present invention relates to magnetic writers. More particularly, the present invention relates to a perpendicular magnetic writer including a write pole having a graded magnetic moment.
The writer portion of a perpendicular recording head typically consists of a main pole and a return pole, which are separated from each other at an air bearing surface of the writer by a gap layer. The main pole and return pole are connected to each other at a region distal from the air bearing surface by a back gap closer or back via. One or more layers of conductive coils are positioned between the main and return poles, and are encapsulated by insulating layers.
To write data to the magnetic media, an electric current is applied to the conductive coils to induce a magnetic field in the media under the main pole. By reversing the direction of the current through the coils, the polarity of the data written to the magnetic media is reversed, and a magnetic transition is written between two adjacent bits. Because the main pole is generally the trailing pole of the main and return poles, the main pole is used to write the data to the magnetic media. Accordingly, it is the main pole that defines the track width of the written data. More specifically, the track width is defined by the width of the main pole at the air bearing surface.
In perpendicular recording heads, magnetization transitions are recorded on the magnetic medium by a trailing edge of the main pole. The shape of the main pole is projected and reproduced on the magnetic medium during the write process. However, unwanted side writing may occur due to the change in skew angle as the recording head travels in an arc across the magnetic medium. This can cause adjacent track interference, resulting in off track erasure of transitions recorded on the magnetic medium. With increasing write pole height, the effect of the skew angle on the write pole is more pronounced, which results in a reduction of the track density on the magnetic medium.